Hematopoietic precursor transplantation or bone marrow transplantation is not without some risks or complications for the person with hematologic deficiencies or diseases, but there are hardly any risks for the donor. Advances in hematology have meant that complications for the recipient have been minimized and the success rate is higher. Hematology experts therefore encourage the population to donate bone marrow, since it is the source of life for many patients.
Complications of bone marrow transplantation
Hematopoietic precursor transplants are not free of side effects. The main ones, in order of frequency, are:
– Infection
Bone marrow transplantation usually requires that the recipient’s own marrow be destroyed (“myeloablation”). Prior to “engraftment” patients may go several weeks without enough white blood cells to help fight infections. This puts the patient at high risk for infections, despite antibiotics.
Immunosuppressive agents used in allogeneic transplants for the prevention or treatment of graft-versus-host disease further increase the risk of opportunistic infection. Immunosuppressive drugs are administered for a minimum of 6 months after transplantation, or longer if necessary to treat graft-versus-host disease. Transplant patients lose their acquired immunity. For this reason, transplant patients should be re-vaccinated once they have completed the immunosuppressive treatment regimen.
– Hemorrhage
The bone marrow produces platelets, which are cell fragments that stick to regions where there are blood vessel injuries, to limit blood loss. Destruction of platelet-producing cells makes severe bleeding more likely. Therefore, many patients require platelet transfusions during the days immediately following transplantation.
– Veno-Occlusive Disease
Severe liver injury can result from veno-occlusive disease (VOD). Elevated bilirubin levels, enlargement of the liver or spleen, and fluid retention are clinical features of this disease. It is characteristic of allogeneic transplants. It is due to generalized cellular injury and obstruction of the hepatic venous sinuses. Severe cases are associated with a high mortality rate. Treatment with anticoagulants may be effective in reducing the severity of VOD but may also increase bleeding complications. A drug has been shown to help prevent VOD by facilitating the flow of bile.
– Mucositis
Mucosal lesions of the mouth or mucositis are a common complication of hematopoietic stem cell transplantation. It is usually not life threatening, but it is painful and does not allow eating and drinking. Mucositis is treated with pain medications, as well as intravenous infusions of fluids to prevent dehydration and malnutrition. It is also treated with laser therapy, which relieves pain and allows the patient to ingest food. Sometimes cold, due to its vasocontrictor effect, prevents the onset of mucositis, so patients are advised to eat ice cream.
– Graft-versus-host disease
Graft-versus-host disease (GVHD) is an inflammatory process characteristic of allogeneic transplantation. It is an attack of the “new” immune cells from the bone marrow against the recipient’s tissues. This can occur even if the donor and recipient are HLA-identical, as the immune system can still recognize other differences between their tissues. High doses of corticosteroids, such as prednisone, are the standard treatment. However, this immunosuppressive treatment often leads to fatal infections. Chronic graft-versus-host disease can also develop after allogeneic transplantation. It is the main source of final treatment-related complications, although it is not usually fatal. In addition to inflammation, it can lead to the development of fibrosis, similar to scleroderma, as it can cause functional disability and requires prolonged immunosuppressive treatment. Graft-versus-host disease is usually mediated by T-lymphocyte-like cells, which react with foreign peptides or antigens from different tissues of the recipient.
Graft-versus-tumor effect
The graft-versus-tumor (GVT) effect or the “graft-versus-leukemia” effect is the beneficial aspect of the graft-versus-host phenomenon. For example, patients with acute or particularly chronic graft-versus-host disease after allogeneic transplantation tend to have a lower risk of cancer recurrence. This is due to a therapeutic immune reaction of the donor T lymphocytes against the diseased bone marrow of the recipient.
GVT is the main benefit of transplants that do not employ the highest immunosuppressive regimens. Graft-versus-tumor is primarily beneficial in slowly progressing diseases such as chronic leukemia, low-grade lymphoma and, in some cases, multiple myeloma. However, it is less effective in acute leukemias, given their rapid expansion and cell growth capacity. If there is a relapse of the cancer after a first transplant, a new transplant can be performed by infusing the patient with an increased amount of white blood cells (T lymphocytes) from donor blood.
Prognosis of bone marrow transplantation
The prognosis varies widely depending on the type of disease, stage, stem cell source, HLA match and conditioning regimen. Transplantation offers a chance of cure or long-term remission if the inherent complications of graft-versus-host disease, immunosuppressive treatments and the spectrum of infections can be survived. In recent years, survival rates have been gradually improving. Mortality for allogeneic transplantation is estimated to be around 35-40%, lower for those transplants with milder ablative regimens, also called mini-allografts (around 15%). Mortality for autologous transplants is low, around 5% of transplants.
Risks for the hematopoietic stem cell donor
The risks for the donor are minimal, and it should be borne in mind that this is the only transplant that would allow the same donor to donate several times, since the marrow or donated progenitors regenerate in 10-15 days. A slight pain or hematoma may appear at the puncture site and sometimes fever that responds perfectly to antipyretics when granulocyte colony-stimulating factor or a cytostatic is administered to move the hematopoietic progenitors to the peripheral blood.
That is why hematology experts encourage the entire population to donate bone marrow or hematopoietic progenitors, as it is the source of life for many patients.